An ionic activity-measuring device utilizing an ion selective electrode is widely employed for analyzing ionic components in a liquid sample such as a whole blood sample or a serum sample.
U.S. Pat. No. 4,571,293 (which corresponds to EP 0 160 997 B1) discloses an ionic activity-measuring device using an ion selective electrode which is illustrated in FIG. 1 of the drawings attached to this specification.
In FIG. 1, the ionic activity-measuring device comprises a non-electroconductive support 11, a pair of electrodes each of which comprises a silver metal layer 12a, 12b and a silver halide layer 13a, 13b, a common electrolytic material layer 14, a common ion selective membrane 15, and a common non-electroconductive cover sheet 16 having a pair of openings 17a, 17b for receiving and keeping a sample solution and a reference solution, respectively, each opening being placed over each electrode unit, and having thereon an a bridge member 18 for electrically bridging the sample solution received in one opening 17a and the reference solution received in another opening 17b. Each silver metal layer 12a, 12b has an exposed surface 10a, 10b, respectively. By placing probes of a potentiometer 19 on these exposed silver metal surfaces 10a, 10b, the produced electric potential difference can be measured.
The ion selective electrode can measure an ionic activity of an ionic component such as H+, Li+, Na+, K+, Mg2+, Ca2+, Cl−, HCO3−, or CO32−, by employing an appropriate ion selective membrane.
U.S. Pat. No. 4,789,435 describes an ion selective electrode assembly comprising plural ion selective electrodes for analyzing plural ionic components such as Na+, K+, and Cl−, simultaneously. In the assembly, one of plural ion selective electrodes has an ion selective membrane differing from that of other ion selective electrode in chemical composition.